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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

IRON

181

being 1-5-2%). They are very rich in carbon (2-5%), which occurs entirely
in the graphitic state in ordinary grey cast-irons, and partly combined in the
lighter ones. They contain also small quantities of manganese (about i%) and
sometimes sulphur (0-01-0-1%) and phosphorus (0-05-1-8%). They serve in
general for foundry purposes and those with little phosphorus for refining.

White cast-irons have a shining, white colour tending to grey, a crystalline,
granular and, sometimes, radiating fibrous structure ; they melt at about 1100
and have the specific gravity 7-4-7-5. They contain 2-3-5% of carbon, largely
combined, and only small quantities of silicon (0-5-1%), but they are very rich
in manganese (1-5%), and sometimes contain considerable proportions of sul-
phur (0-1-0-25%) and phosphorus (more than 3%). They are usually employed
for refining.

The products containing more than 5 % of manganese are : Spiegeleisen (5-30 %
Mn, 0-2-1-2% Si and 4-5% C), Silico-Spiegel (20% Mn, 10-12% or even more Si),
and Ferro-manganese (30-85% Mn and up to 7-5% C).

Malleable iron represents the product of the refining of cast-iron, contains
less than 2 % of carbon and, according to its carbon content, to its uses, and to
its hardness, elasticity, strength, etc., is subdivided into : soft iron (soft wrought-
iron or mild steel, according to the mode of preparation), which is very ductile
and malleable and contains less than 0-3-0-5% of carbon ; and steel (cementa-
tion or blister steel, crucible steel, cast steel, etc.), which has larger amounts of
carbon (more than 0-3-0-5%) and is ductile and malleable, but very hard, elastic
and resistant and capable of being hardened. Steels with more than 1-5%
of carbon begin to lose their malleability and become brittle.

Small quantities of silicon increase the hardness of malleable iron but dimin-
ish its malleability (a good malleable iron should not contain more than o-i-
0-2%). Most harmful for malleable iron are phosphorus, which even in small
quantities (0-1%) renders it cold short, and sulphur, which renders it red short
even in the proportion of 0-05-0-1%. Manganese diminishes the harmful
effects of sulphur and hence improves the quality of iron and steels. Injuri-
ous actions are also exerted by arsenic, tin, antimony, copper (beyond 0-4%),
oxygen, etc.

The following table gives the compositions of various commercial types of
soft iron and steel.

TABLE VIII
Compositions of Various Iron and Steels (percentages)


	C
	Si
	Mn
	P
	S

Swedish iron    .
	0-02-0-07
	<J3-O 1-0-02
	0-0-15
	Trace-o-o2
	0-OI-O-O2

Wrought-iron  .
	0-16
	O-O2
	0-09
	0-09
	Trace

Wrought steel .
	0-90
	O-IO
	0-25
	0-07
	Trace

Ingot iron for construc-
	
	
	
	
	

tion   ......
	0-08-0-25
	<fo-O2
	0-4-0-6
	<"o-o8
	<o-o8

Ingot steel for rails
	0-30-0-50
	O-O5-O-2O
	0-5-1-0
	<o-o8
	<p-o8

Martin steel for castings
	0-30-0-60
	0-2O-O-6O
	0-5-1-0
	o-i
	

Crucible tool steel .
	0-7-1-2
	0-1-0-2
	0-1-0-3
	<o-04
	<o-03

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